Please help me understand the difference between the side adjustment parallax and the adjustable objectives on longer range scopes. I am left handed and wanting to buy a new scope for use in 300-1,000 yard shots. I like the adjustable objective scopes over the (side focus) parallax scopes as I can use them with my right hand. I am looking at a couple of scopes and like both but as I said I prefer the AO over the Parallax adjustments. What suggestions do you have? Vortex Viper 6.5-20X50 Leupold VX-3 6.5-20X40 AO, with added target turrets Leupold || VX-3 6.5-20x40mm Adj. Obj.